1. Field of the Invention
The invention relates to a valve assembly and method for controlling flow of gases from an engine crankcase to an engine intake manifold.
2. Background of the Invention
Positive crankcase ventilation (PCV) valves have long been used to remove crankcases gases from the crankcase of an engine. Crankcases gases are a combination of (i) blowby gases, (i.e., combusted and non-combusted combustion chamber gases which migrate past piston rings into the crankcase), (ii) fuel, (iii) air, and (iv) oil vapor. PCV valves regulate the removal of crankcase gases from the crankcase by venting the gases into the engine intake manifold.
One known PCV valve is disclosed in U.S. Pat. No. 3,709,204. The known PCV valve shuts off the flow of gases from a crankcase to an intake manifold until the temperature of the engine has increased above a predetermined temperature. In particular, the known valve shuts off flow of the gases during cold engine starting. Another similar PCV valve system is disclosed in U.S. Pat. No. 3,263,660 that shuts off flow during cold engine starting.
The inventors herein have recognized that there are several disadvantages with stopping the flow of crankcase gases from a crankcase to an intake manifold during cold operating conditions. First, the inventors herein have recognized that during cold operating conditions, crankcase gases are more likely to react with oil to form sludge, which in turn can adversely effect the oil lubrication properties resulting in increased engine wear. Thus, stopping the flow of fresh air into the crankcase can increase the tendency of engine oil sludge formation. Second, the inventors herein have recognized that because a byproduct of combustion is water, the crankcase gases are relatively humid. Thus, stopping the flow of fresh air into the crankcase results in a relatively high crankcase humidity where the water vapor can freeze within the PCV valve during cold operating conditions. This ice formation can adversely effect the operation of the PCV valve until the valve is de-thawed.
The foregoing problems and disadvantages are overcome by a valve assembly and method for controlling flow of gases from an engine crankcase to an intake manifold in accordance with the present invention.
A method for controlling flow of gases through a passage between an engine crankcase and an engine intake manifold according to a first aspect of the present invention is provided. The method includes increasing a flow of gases through the passage between the crankcase and the intake manifold when a temperature of the gases is below a predetermined temperature.
A valve assembly for controlling flow of gases through a passage between an engine crankcase and an engine intake manifold in accordance with a second aspect of the present invention is provided. The valve assembly includes a housing configured to be coupled with the passage. The valve assembly further includes a flow control device disposed in the housing. The device increases a flow of the gases through the housing when a temperature of the gases is below a predetermined temperature.
A control system for controlling flow of gases through a passage between an engine crankcase and an engine intake manifold according to a third aspect of the present invention is provided. The control system includes a temperature sensor generating a first signal indicative of a temperature of the engine. The control system further includes a valve assembly having a housing and a flow control device disposed in the housing. The housing is configured to be coupled with the passage. The flow control device is configured to increase a flow of the gases through the housing responsive to a second signal. Finally, the control system includes a controller operably connected to the temperature sensor and the valve assembly. The controller generates the second signal when the first signal indicates the temperature is below a predetermined temperature.
The valve assembly, control system, and method for controlling the flow of gases from an engine crankcase to an intake manifold has several advantages over known systems. In particular, the valve assembly and method increases a flow of crankcase gases through the passage between the crankcase and the intake manifold when a temperature of the gases is below a predetermined temperature to reduce and/or eliminate (i) freezing and development of ice blockages within the valve assembly, and (ii) sludge formation from trapped crankcase gases reacting with engine oil.